Another suggestion
I had the same problem on the 40.5. There is no place to mount the square dingy motor mount. I solved it by using a pvc "T" for a sprinkler line, a 1" dowel and one stainless hose clamp. Just cut the plastic "T" horozontally, through the bottom of the T and almost throgh the top of the T. Slide it over the rail and cut the dowell long enogh to extend from the bottom of the motor mount and into the "T". Bolt the mount in place, stick the dowell in place and clamp the "T", and you are done. The fix costs a about $5 plus the cost of the motor mount, a LOT less then the Edson mount.